Earth System Engineering - A Way Out of Trouble or a Cure

Worse than Disease?

K. KasturiranganMember

Planning CommissionGovernment of India

New Delhi

Foundation Day Lecture Ministry of Earth Sciences

Government of IndiaNew Delhi

July 27, 2009

Earth System Engineering – A Way Out of Trouble or a Cure

Worse Than Disease?• Describes proposals to deliberately manipulate the earth’s climate to

counter-act the effects of global warming from Green House Gas emissions.

• These are not suggested as alternative to emissions control but rather an accompanying strategy.

• Current surge of interest in this area arises from the fact that global warming could be both real and dangerous.

• Notably a complex discipline requiring collation of knowledge in

Scientific disciplines including Atmospheric Chemistry, Ecology, Meteorology and Plant Biology.

Engineering disciplines including Aeronautical Engineering, Naval Architecture & Ballistics.

Management and control disciplines such as risk management and operational research.

Source: IPCC AR4 Ch.6

The rate of increase of population in the last 2000 years (right) is very similar to the rate of increase in the radiative forcing due to greenhouse gases (inset).

Systems Approach: Interactions among components, feedbacks, affecting the total system

Source: IPCC AR4

Inference:The effect of external forcings cannot be ignored; these are unpredictable and may hinder geoengineeringefforts

Comparison between temperature rise as derived from models and observations since the year 1860

Systems Approach

• Interactions and feedbacks among components and these affect the whole system

• Known feedbacks: ice-albedo(+), vegetation (-), cloud-solar radiation(-); cloud-terrestrial radiation (+); Water vapour(+); CO2 -weathering (-); aerosol-clouds-precipitation

• Both external and internal forcings must be taken into account

• Non-linear responses/Thresholds have to be identified and quantified

Inadequacy of models• Models solve partial differential equations that are sensitive to

the initial conditions; small differences in initial conditions may lead to widely different solutions.

• Models do not parameterize all the feedbacks in the Earth System. Models have low spatial resolution.

• Most feedbacks require accurate quantification before they can be incorporated in the models.

• The more sophisticated the model, the more is the requirement for field data (specifically over tropics).

• Illustration with Paleocene Eocene Thermal Maximum (PETM).

1. Palaeoanalogue of Global change?

2. Models unable to predict the warming in high latitudes: clouds that form in high CO2 atmosphere could be different?

3. PETM: ΔT =10 to 30ka atmospheric warming of 5 to 6°C

Source: IPCC AR4 Ch.6

Geoengineering ideas proposed

Carbon Sequestration

(i) Afforestation (ii) Direct CO2 capture

(iii) Petrification of CO2 (iv) Ocean fertilization

Changing the Earth’s effective Albedo(i) Space mirrors (ii) Stratospheric sulphur aerolsols (iii) stratospheric balloons with alumina aerosols (iv) Low stratospheric dust/soot (iv) stimulation of white clouds (v) cool roofs

Removal of atmospheric CFCs

The advantages of global warming include intensifictaion of the hydrological Cycle by water vapour feedback: increased monsoon is expected, and fertilization of plants.

Attennuation of insolation might adversely impact these benefits, e.g. Monsoons, a concern for Asian countries; on the other hand, they might benefit by reduction in extreme weather events

SSTs have increased in the recent years (blue) and so have the destructive power of cyclones (green).

Partition of Anthropogenic Carbon Emissions into Sinks

Canadell et al. 2007, PNAS

Ocean removes ~ 24% Land removes ~ 30%55% were removed by natural sinks

45% of all CO2 emissions accumulated in the atmosphere

The Airborne FractionThe fraction of the annual anthropogenic emissions that remains in the atmosphere

AtmosphereAtmosphere

[2000-2006]

13

• Plankton grow, mature and die—taking carbon with them to the deep ocean

• They have a larger effect on climate than any single other process or group of organisms.

• Of the ~750 billion tons of CO2 that turn over annually, plankton process 45%

• 99% of marine life relies on plankton—they form the base of the marine food chain.

THE BIOLOGICAL PUMP

45% of annual carbon flux is processed by phytoplankton

• “The efficiency of natural sinks has decreased by 10% over the last 50 years (and will continue to do so in the future), implying that the longer we wait to reduce emissions, the larger the cuts needed to stabilize atmospheric CO2.”

• “All of these changes characterize a carbon cycle that is generating stronger climate forcing and sooner than expected.”

Conclusions about the ocean sink from the Global Carbon Project:

Canadell et al. 2007, PNAS

• Part of the decline is attributed to up to a 30% decrease in the efficiency of the Southern Ocean sink over the last 20 years.

• This sink removes annually 0.7 Pg of anthropogenic carbon.

• The decline is attributed to the strengthening of the winds around Antarctica which enhances ventilation of natural carbon-rich deep waters.

• The strengthening of the winds is attributed to global warming and the ozone hole.

Causes of the decrease in efficiency of the ocean sink

Le Quéré et al. 2007, Science

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Iron experiments in world Ocean from 1993-2005

An oceanic phytoplankton bloom

in the South Atlantic Ocean, off

the coast of Argentina.

Encouraging such blooms with

iron fertilization could lock up

carbon on the seabed

Source: Moderate Resolution Imaging

Spectroradiometer (MODIS) on NASA’s Aqua

satellite

Comparison of iron fertilization experiments

0

50

100

150

200

250

300

IronEx II SEEDS SERIES SOIREE EisenEx SOFEXNorth

SOFEXSouth

EIFEX

MLD

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MLD (m)Chl a (mg m-2)Chl a (mg m-3)

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* = duration of experiment in days

How much CO2 can the biological pump sequester in the Southern Ocean?

If ALL the nitrate in the mixed layer (~150m) were converted into phytoplankton biomass,

and if all this biomass sank out of the mixed layer

and if all the resultant CO2 deficit were compensated by uptake from the atmosphere

then

The maximum amount of CO2 that could be sequestered would amount to about 1 (one) Gigatonne of CO2

Equivalent to ~15 % of annual input by humans

This maximum amount could be removed about once every 4 years.

Source:Victor Smetacek

Ocean acidification affects the growth of calcifying organisms: Calcification and shell growth rates – coccolithophoridae. The efficiency

of the oceans for uptake of CO2 is thus reduced significantly.

Courtesy: Zondervan et al 2001

Change in sea surface pH caused by anthropogenic CO2 between the 1700s and

the 1990s. This ocean acidification will still be a major problem unless atmospheric

CO2 is reduced.

Source: Global Ocean Data Analysis Project & World Ocean Atlas Climatologies

Courtesy: Rost and Riebesell 2004, (Springer)

Varying Photosynthetic response of biota in the sea

Some of these may be more effective in removing CO2 from the atmosphere. The relative geographical distribution of various species and the overall efficiency for

CO2 removal is yet to be quantified.

Conclusions• Viable options:

(i) Use alternative energy sources, fuel-efficient

engines to control emissions, prevent direct

emissions (ii) afforestation (land) and

fertilization (ocean) to scavenge CO2 from the

atmosphere (iii) Peterification of CO2 by

reaction with peridotite.

• Coordinated research to precisely quantify

various feedbacks (e.g. soil carbon residence

times, extreme weather events)